Heretofore, a key pressing input method of pressing a key that imparts a sense of click in inputting was prevalently used in this country as a letter/character inputting method for a mobile electronic device. Recently, such a mobile electronic device carrying a touch panel of a large format is becoming popular globally such that its share on the market is increasing in Japan as well. As the mobile electronic devices, carrying the touch panel, become popular, an increasing number of the mobile electronic devices use a touch input method in which the touch panel is touched for inputting. In light of the above, it has been proposed that both a key pressing input method and a touch input method may selectively be used in legacy electronic devices (see Patent Literatures 1 and 2).    [Patent Literature 1] JP Patent Kokai Publication No. JP-P2002-244791A    [Patent Literature 2] JP Patent Kokai Publication No. JP-P2007-60074A    [Patent Literature 3] JP Patent Kokai Publication No. JP-A-9-23261